1. Field of the Invention
The present invention relates to a signal transferring system and method thereof, and more particularly to a signal transferring system with unequal transferring paths and method thereof.
2. Description of the Prior Art
The constantly increasing system operating frequency of electronic apparatuses has resulted in many challenges when designing an interface between electronic apparatuses. For example, the input/output interface of a DDR SDRAM (Double Data Rate SDRAM) has to operate at a high speed (i.e. ≧100 MHz) clock, in which two data bits should be read in a single clock cycle. In other words, one data bit is read in the rising edge and the other data bit is read in the falling edge of the clock. Therefore, the reading time of one data bit is relatively short. Accordingly, the phases of the clock and data have to be locked precisely in order to read the data accurately. Furthermore, the input/output interface of the memory is required to utilize the pulse of a data strobe signal for sampling the 8 bits/16 bits data (DQ), therefore the layout lengths for the data signal and the relative data strobe signal on the circuit board have to be the same. Larger amounts of layout numbers, higher data transmitting speed, and more complicated operation of the circuit system will increase the difficulty of designing the circuit board. Furthermore, for the sake of equalizing the delay time of each layout path, the layout on the circuit board should be designed to have the shortest possible lengths and smallest possible area. The transmission line effect that emerges when operating at a high data speed will affect the normal operation of the electronic apparatus. Moreover, because the data of the DDR memory is transmitted at very high speeds, (8 bits/16 bits at a time), the power/ground bouncing noise that emerges at the input/output pad of the memory controller will seriously damage the signal accuracy of the analog circuit within the SoC (System on Chip) device, such as a digital to analog converter.